I'm willing to place some historical blame for the current situation on every POTUS since Hoover.
But clearly in that narrative there is a key date that sticks out -2006- when they exploded their first bomb. You could certainly say that is the point where the US should have acted, before there were more and better delivery systems.
Unfortunately if we go back to that date in the wayback machine we find the US on the brink of losing the war it chose in Iraq*, bogged down in AFG and having blown through every bit of its international moral capital faster than Tiffany Trump will go through her inheritance.
Just a bit of nitpicking there regarding Trump's "25 years" narrative.
*another of "the axis of evil" as GWB decided we weren't going to pussyfoot around any more. Unfortunately buying a big hat at the dime store doesn't make you sheriff and being a reality TV and WWE star doesn't make you a leader.
Re: Korea nukes
although I'll grant one thing to the graduates of the Sarah Palin School of Foreign Relations at Wasilla
Prior to 1991 NK was a very closely held Soviet client state and it was just a small part of the larger game and nobody was going to risk WWIII over it.